There appears to be a relevant debate going on regarding the accuracy of GFS PRMSL after smoothing is applied. It is claimed that the smoothing of PRMSL reduces resolution of the isobars significantly and this can lead to inaccurate forecasting.

My understanding is that UEMS initializes with PRMSL when using GFS data. The personal tile server (gfsp25pt) includes MSLET in the initialization gribs but is it being used?
How can one force prep into using MSLET and to disregard PRMSL?

David

Last edited by norulz on Mon Sep 03, 2018 11:46 am, edited 2 times in total.

Thanks for raising this issue. It's easy to use MSLET. 1) Make sure MSLET is in your GFS grib2 file and 2) edit the Vtable.GFS by finding the line for Sea-level pressure (PMSL) and change the GRIB2 param (next to last column) from 1 to 192. That's it.

I've tested it on a hurricane case using ARW and it produces only minor changes in the forecast. The reason for that is because while PRMSL is smoothed, all the other fields (U, V, T, Q, and GHT) are not. The model quickly adjusts to the state given by U, V, T, Q, and GHT.

In the poster, the authors are talking about forecasts made from plots of the GFS PRMSL. Not about numerical forecasts initialized from PRMSL. Nevertheless, it's probably best to use MSLET now that NCEP supplies it.